U.S. patent application number 17/285270 was filed with the patent office on 2021-12-02 for optical particle sensor, in particular, exhaust gas sensor.
This patent application is currently assigned to Robert Bosch GmbH. The applicant listed for this patent is Robert Bosch GmbH. Invention is credited to Enno Baars, Martin Buchholz, Radoslav Rusanov, Johannes Weber.
Application Number | 20210372886 17/285270 |
Document ID | / |
Family ID | 1000005835599 |
Filed Date | 2021-12-02 |
United States Patent
Application |
20210372886 |
Kind Code |
A1 |
Baars; Enno ; et
al. |
December 2, 2021 |
OPTICAL PARTICLE SENSOR, IN PARTICULAR, EXHAUST GAS SENSOR
Abstract
A particle sensor for detecting particles in a flow of a
measuring gas for detecting soot particles in an exhaust gas
channel of a burner or of an internal combustion engine. The
particle sensor includes a device for generating or for supplying
laser light, a device for focusing laser light, and a device for
detecting or transferring thermal radiation. The particle sensor
includes at least one optical access, which separates an area
exposed to the measuring gas from an area facing away from the
measuring gas not exposed to the measuring gas, the device for
generating or supplying laser light and/or the device for detecting
or for transferring thermal radiation being situated in the area
facing away from the measuring gas, wherein the particle sensor
removes a sub-flow from the measuring gas flow and supplies it to
the laser focus and further fluidically shields the optical access
from the sub-flow.
Inventors: |
Baars; Enno; (Leonberg,
DE) ; Weber; Johannes; (Stuttgart, DE) ;
Buchholz; Martin; (Bietigheim-Bissingen, DE) ;
Rusanov; Radoslav; (Stuttgart, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Robert Bosch GmbH |
Stuttgart |
|
DE |
|
|
Assignee: |
Robert Bosch GmbH
Stuttgart
DE
|
Family ID: |
1000005835599 |
Appl. No.: |
17/285270 |
Filed: |
September 20, 2019 |
PCT Filed: |
September 20, 2019 |
PCT NO: |
PCT/EP2019/075369 |
371 Date: |
April 14, 2021 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01N 15/0205 20130101;
G01N 2015/0046 20130101; G01M 15/108 20130101 |
International
Class: |
G01M 15/10 20060101
G01M015/10; G01N 15/02 20060101 G01N015/02 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 31, 2018 |
DE |
102018218734.7 |
Claims
1-14. (canceled)
15. A particle sensor for detecting particles in a flow of a
measuring gas, comprising: a device configured to generate or
supply laser light; a device configured to focus the laser light; a
device configured to detect or transfer thermal radiation; and at
least one optical access, which separates an area exposed to the
measuring gas from an area not exposed to the measuring gas;
wherein the device configured to generate or supply laser light
and/or the device configured to detect or transfer thermal
radiation is situated in an area facing away from the measuring
gas; and wherein the particle sensor is configured to remove a
sub-flow from the flow of the measuring gas and supply the sub-flow
to a laser focus, and to fluidically shield the optical access from
the sub-flow.
16. The particle sensor as recited in claim 15, wherein the
particle sensor is for detecting soot particles in an exhaust gas
channel of a burner or of an internal combustion engine.
17. The particle sensor as recited in claim 15, wherein the
particle sensor includes a housing, in or at which the optical
access is situated, and the housing including at least one inlet
opening, through which the sub-flow is removable from the flow of
the measuring gas, and introducible into the interior of the
housing, and including at least one outlet opening, through which
the sub-flow exits the housing, and a shielding being provided in
an interior of the housing, which redirects the sub-flow in a
direction oriented away from the optical access.
18. The particle sensor as recited in claim 17, wherein the
shielding redirects the sub-flow from a direction oriented toward
the optical access in a direction oriented away from the optical
access.
19. The particle sensor as recited in claim 18, wherein the
shielding redirects the sub-flow, from a direction oriented from
the inlet opening toward the optical access in a direction oriented
away from the optical access to the outlet opening.
20. The particle sensor as recited in claim 17, wherein the housing
includes a housing body, in or at which the optical access is
situated, and the housing further includes a protective tube
module, which is fastened at the housing body or is integrated with
the housing body, and includes at least one inlet opening, through
which the sub-flow is removable from the flow of the measuring gas
and introducible into an interior of the protective tube module,
and includes at least one outlet opening, through which the
sub-flow exits the protective tube module, and a shielding is
provided in the interior of the protective tube module, which
redirects the sub-flow in a direction oriented away from the
optical access.
21. The particle sensor as recited in claim 20, wherein the
protective tube module includes a first protective tube, which
includes the at least one inlet opening through which the sub-flow
is removable from the flow of the measuring gas and introducible
into the interior of the protective tube module, and the protective
tube module includes a second protective tube which is situated in
the first protective tube in such a way that an annular space is
formed between the first protective tube and the second protective
tube, and the second protective tube includes at least one overflow
opening through which the sub-flow flows from the annular space
into a gas space situated in an interior of the second protective
tube, and the outlet opening is formed at the first protective tube
or at the second protective tube, and a device is provided which is
configured to redirect the sub-flow as the sub-flow flows through
or after it flows through the overflow opening in a direction
oriented away from the optical access to the outlet opening.
22. The particle sensor as recited in claim 21, wherein the device
configured to redirect the sub-flow as the sub-flow flows through
or after it flows through the overflow opening in a direction
oriented away from the optical access to the outlet opening, is at
least one swirl flap formed at the overflow opening of the second
protective tube, which points in a direction oriented away from the
optical access to the outlet opening or is a third protective tube
which is situated in the second protective tube and tapers in a
conical or step-like manner in the direction pointing from the
optical access to the outlet opening at a level of the overflow
opening or is a recess formed in an end face of the housing body
pointing away from the optical access which is situated opposite
the overflow opening of the second protective tube.
23. The particle sensor as recited in claim 22, wherein the recess
is a groove.
24. The particle sensor as recited in claim 21, wherein the device
configured to redirect the sub-flow as the sub-flow flows through
or after it flows through the overflow opening in a direction
oriented away from the optical access to the outlet opening,
completely or partially hinders a visibility of the optical access
as viewed from the inlet opening and/or from the overflow
opening.
25. The particle sensor as recited in claim 20, wherein the outlet
opening is formed at an end face of the protective tube module
pointing away from the housing body, and the inlet opening is
situated, as viewed from the optical access, in front of the outlet
opening in the direction pointing from the optical access to the
outlet opening.
26. The particle sensor as recited in claim 17, wherein the at
least one inlet opening includes multiple inlet openings, all of
which are situated at the same level in a direction pointing from
the optical access to the outlet opening.
27. The particle sensor as recited in claim 26, wherein the at
least one inlet opening includes 6 to 12 inlet openings, all of
which are situated at the same level in a direction pointing from
the optical access to the outlet opening
28. The particle sensor as recited in claim 21, wherein the at
least one overflow opening of the second protective tube includes
multiple overflow openings, all of which are situated at the same
level in the direction pointing from the optical access to the
outlet opening.
29. The particle sensor as recited in claim 21, wherein the at
least one overflow opening of the second protective tube includes 4
to 12 overflow openings, all of which are situated at the same
level in the direction pointing from the optical access to the
outlet opening.
30. The particle sensor as recited in claim 25, wherein the at
least one overflow opening of the second protective tube includes
multiple overflow openings, all of which are situated at the same
level in the direction pointing from the optical access to the
outlet opening, and wherein the inlet openings are all situated, as
viewed from the optical access, behind the overflow opening in the
direction pointing from the optical access to the outlet
opening.
31. The particle sensor as recited in claim 15, wherein the laser
focus is situated outside the fluidically shielded area.
32. The particle sensor as recited in claim 15, wherein the device
configured to generate laser light is a laser and/or the device
configured to supply laser light is an optical fiber and/or the
device configured to focus is the optical access configured as a
lens, and/or the device configured to detect thermal radiation is a
photodetector and/or the device configured to transfer thermal
radiation is an optical fiber and/or the optical access is a window
or an optical fiber.
Description
FIELD
[0001] The present invention relates to a particle sensor for
detecting particles in a flow of a measuring gas, in particular, to
a sensor for detecting soot particles in an exhaust gas channel of
a burner or of a self-igniting or spark-ignited internal combustion
engine, as it may be used, for example, for the purpose of the
on-board diagnosis of a corresponding soot particle filter. Other
fields of application are, of course, also possible, for example,
portable systems for monitoring emissions and systems for measuring
ambient air quality.
BACKGROUND INFORMATION
[0002] German Patent Application No. DE 10 2017 207 402 A1 involves
a soot particle sensor including a laser module that includes a
laser and including a detector configured to detect thermal
radiation. The soot particle sensor described therein is
distinguished by the fact that the laser is configured to generate
laser light and that the soot particle sensor includes an optical
element situated in the beam path of the laser, which is configured
to bundle laser light emanating from the laser module into one
spot, and that the detector is situated in the soot particle sensor
in such a way that it detects radiation emanating from the
spot.
[0003] The sensor described in German Patent Application No. DE 10
2017 207 402 A1 describes the measuring principle of laser-induced
incandescence.
[0004] In German Patent Application No. DE 10 2017 207 402 A1, it
is further also provided that the soot particle sensor is
subdivided into a first part, which is configured to be exposed to
a measuring gas, and in a second part not to be exposed to the
measuring gas, which contains the optical components of the soot
particle sensor, both parts being separated by a separating wall
impermeable to the measuring gas, and in that a window, which is
transparent both for the laser light as well as for the radiation
emanating from the spot, is mounted in the beam path of the laser
light.
SUMMARY
[0005] The present invention is based on the observation of the
inventors that in a particle sensor, the optical access of the
particle sensor may be contaminated over its service life. In this
case, it has been found that under adverse conditions, the
contamination may progress to the point that a sufficient
transparency of the optical access for laser light and thermal
radiation is no longer ensured, and the particle sensor no longer
functions properly.
[0006] According to an example embodiment of the present invention,
it is therefore provided that the particle sensor removes a
sub-flow from the measuring gas flow and supplies it to the laser
focus, and furthermore fluidically shields the optical access from
the sub-flow. In this way, a sub-flow which is representative of
the measuring gas flow with respect to its particle content, is fed
to the laser focus, i.e., to the actual location of the particle
detection. However, the optical access is shielded from the
measuring gas flow as well as from the sub-flow, i.e., the
measuring gas flow and the sub-flow do not flow against the optical
access, and contaminants, for example, soot particles, contained in
the measuring gas flow and sub-flow are unable to reach the optical
access. Thus, a contamination of the optical access no longer
occurs or occurs only to a tolerable degree over the service life,
and in this respect the service life of the particle sensor is not
limited or significantly increased.
[0007] The detection of particles is understood within the scope of
the present invention to mean, in particular, a measurement, whose
result is the mass and/or the number of particles and/or the mass
and/or the number of particles in a flow per unit time, in
particular, at the location of the laser focus. The detection of
particles may also include the obtainment of pieces of information
relating to the size and/or to the size distribution of the
particles.
[0008] Means (e.g., a device) for generating laser light is
understood within the scope of the present invention to mean, in
particular, a laser, for example, a diode laser, in particular, a
CW laser, whose output power and focusability are so high that it
is able to excite soot particles for emitting thermal radiation,
for example, at above 3500 K.
[0009] Means (e.g., a device) for supplying laser light is
understood within the scope of the present invention to mean, in
particular, an optical fiber, which is transparent to the relevant
laser light, and/or an optical window, which is transparent for the
laser light. The laser light may be, for example, ultraviolet,
visible or infrared.
[0010] Means (e.g., a device) for focusing laser light is
understood within the scope of the present invention to mean, in
particular, a convergent lens, which is transparent for the
relevant laser light. Alternatively, it could also be a concave
mirror.
[0011] Means (e.g., a device) for transferring thermal radiation is
understood within the scope of the present invention to mean, in
particular, an optical fiber, which is transparent for the relevant
thermal radiation, and/or an optical window, which is transparent
to the relevant thermal radiation. Thermal radiation is understood
within scope of the present invention to mean, in particular:
electromagnetic radiation, corresponding to the emission of hot
bodies, for example, incoherent infrared and/or visible
radiation.
[0012] An optical access is understood within the scope of the
present invention to mean, in particular, an optical fiber or an
optical window. The optical access may, in particular, also fulfill
the function of the means for focusing laser light, it may be
designed, for example, as a convergent lens.
[0013] The removal of a sub-flow from the measuring gas flow is
understood within the scope of the present invention to mean, in
particular, that a portion of the measuring gas flow, namely, the
sub-flow, is diverted into the interior of the particle sensor,
whereas the remaining other portion of the measuring gas flow flows
past the particle sensor without entering into its interior. The
sub-flow may also be assembled of multiple individual flows, which
enter separately from one another into the interior of the particle
sensor.
[0014] Within the scope of the present invention, inlet openings
and overflow openings may have diameters of 1 to 3 mm or may have
corresponding cross sectional areas in the case of non-circular
geometry.
[0015] The fluidic shielding of the optical access from the
sub-flow is understood within the scope of the present invention to
mean, in particular, a fluid-dynamic shielding, i.e., understood to
mean that the sub-flow is diverted in such a way that it does not
encounter the optical access or, in other words, that an area not
flowed through by the sub-flow remains in front of the optical
access. This may be reflected, in particular, by the fact that the
area not flowed through represents in terms of the transport
phenomena a diffusion-dominated flow area, in contrast to the areas
flowed through in the interior of the sensor, which in this respect
should be referred to as convection-dominated flow areas.
[0016] The fluidic shielding of the optical access may take place
using particular constructive measures, which are explained by way
of example but not exhaustively below in the exemplary
embodiments.
[0017] In one refinement of the present invention, it is provided
that the particle sensor includes a, for example, metallic housing,
in or at which the optical access is situated, and that the housing
includes at least one inlet opening through which a sub-flow is
removable from the flow of the measuring gas and introducible into
the interior of the housing, and that the housing includes at least
one outlet opening, through which the sub-flow exits the housing,
and that a shielding is provided in the interior of the housing,
which redirects the sub-flow in a direction oriented away from the
optical access, i.e., prevents, in particular, via the redirection
the optical access from being affected by the sub-flow and/or
ensures that the optical access is not affected by the
sub-flow.
[0018] The redirection of the sub-flow for the purpose of shielding
the optical access thus takes place, in particular, from a
direction oriented toward the optical access in a direction
oriented away from the optical access; the sub-flow would have
acted on the optical access had the measure effectuating the
redirection or the shielding not been provided.
[0019] The redirection may take place, in particular, from a
direction oriented from the inlet opening toward the optical access
in a direction oriented away from the optical access to the outlet
opening.
[0020] The redirection may take place, in particular, from a
direction oriented from an overflow opening (see below) toward the
optical access in a direction oriented away from the optical access
to the outlet opening.
[0021] In one refinement of the present invention, it may be
provided that the housing of the particle sensor includes a housing
body and a protective tube module fastened to the housing body.
[0022] The housing body may, for example, be a massive steel
component including a through-channel in its interior, which
includes a thread, in particular, an external thread, and a
mounting profile, for example, an external hexagonal profile. A
two-part design of the housing body is also possible, in which a
cap nut/cap screw including the thread and the assembly profile is
slid onto a housing body sleeve.
[0023] The protective tube module may, for example, include
multiple protective tubes, which are produced from sheet steel, and
of which at least one or all are fastened to the housing body, for
example, are welded and/or are inserted into the housing body. The
protective tubes may also be welded with one another or inserted
into one another, in particular, compressed.
[0024] A one-part design of the housing body including the
protective tube module is advantageous.
[0025] In a refinement in accordance with an example embodiment of
the present invention for providing a protective tube module, it is
provided that the protective tube module includes at least one
inlet opening, through which a sub-flow is removable from the flow
of the measuring gas and introducible into the interior of the
protective tube module, and includes at least one outlet opening,
through which the sub-flow exits the protective tube module.
[0026] The inlet opening or inlet openings and the outlet opening
or outlet openings and an overflow opening or overflow openings
(see below) may be designed as holes in the protective tube module
or in the individual tube modules. Swirl flaps may also be added in
each case, which are, in particular, rigid formations on the
protective tube module or on a protective tube and which guide
and/or redirect the sub-flow when flowing through the holes in a
predefined direction. The combination of a hole including a swirl
flap may, for example, be manufactured by cutting or impressing
sections in the protective tube module or in the individual
protective tubes.
[0027] It is provided in accordance with an example embodiment of
the present invention, in particular, that a shielding is provided
in the interior of the protective tube module, through which the
fluidic shielding of the optical access from the sub-flow, in
particular, as explained above, takes place. Thus, with the aid of
a fluidic shielding, a redirection of the sub-flow, in particular,
takes place in a direction oriented away from the optical access.
In the absence of the shielding, the sub-flow would, in particular,
have acted on the optical access and particles contained in the
sub-flow would have potentially contaminated, in particular, the
optical access.
[0028] In one advantageous refinement of the present invention, the
protective tube module includes at least two protective tubes,
namely, a first protective tube and a second protective tube.
[0029] In this case, the first protective tube may include at least
one inlet opening, through which a sub-flow is removable from the
flow of the measuring gas and introducible into the interior of the
protective tube module.
[0030] The second protective tube may be situated in the interior
of the first protective tube in such a way that an annular space is
formed between the first and the second protective tube. The first
and the second protective tube may have as a basic shape (i.e.,
apart from holes, swirl flaps and manufacturing-related minimal
dimensional deviations) an axial symmetry and, in this respect, be
situated concentrically or coaxially to one another.
[0031] The second protective tube may also include at least one
overflow opening, through which the sub-flow flows from the annular
space into a gas space situated in the interior of the second
protective tube.
[0032] The outlet opening may be formed at the first or at the
second protective tube, in particular at an end face of the
particle sensor located at a measuring gas side of the optical
access. It may, in particular, be a single outlet opening.
[0033] In this context, a means (e.g., a device), in particular, is
provided, which redirects the sub-flow, as it flows through or
after it flows through the overflow opening, in a direction
oriented away from the optical access and, in particular, toward
the outlet opening. This means corresponds, in particular to the
fluidic shielding previously mentioned above. Reference is made to
the corresponding explanations.
[0034] Such a means, which redirects the sub-flow as it flows
through or after it flows through the overflow opening in a
direction oriented away from the optical access and, in particular,
toward the outlet opening, may be implemented in various ways.
[0035] According to one specific embodiment of the present
invention, this means is implemented by at least one swirl flap
designed at the overflow opening of the second protective tube,
which points in a direction away from the optical access and, in
particular, toward the outlet opening. Thus, the sub-flow enters
here into the gas space already at a direction oriented away from
the optical access. It therefore does not act on the optical
opening.
[0036] According to another specific embodiment of the present
invention, this means is implemented by a third protective tube,
which is situated in the second protective tube. It may be a third
protective tube, which tapers in a conical or step-like manner at
the level of the overflow opening in the direction pointing from
the optical access to the outlet opening. The sub-flow, after
flowing through the overflow opening, encounters in this case the
third protective tube and the sub-flow is redirected away from the
optical access due to the tapering geometry of the protective
tube.
[0037] According to yet another specific embodiment of the present
invention, this means is implemented by a recess, for example, a
groove, formed in an end face of the housing body pointing away
from the optical access, which is situated opposite the overflow
opening of the second protective tube. The recess, for example, the
groove, redirects the sub-flow after the sub-flow flows through the
overflow opening, for example, by up to 180.degree., away from the
optical access and, in particular, toward the outlet opening.
[0038] As a result, a means may also be qualified to redirect the
sub-flow as it flows through or after it flows through the overflow
opening in a direction oriented away from the optical access and,
in particular, toward the outlet opening, so that as viewed from
the inlet opening and/or from the overflow opening, it hinders the
visibility of the optical access. In other words: The means is
situated geometrically between the inlet opening and the optical
access and/or between the overflow opening and the optical access.
This feature may relate to the entire spatial extension of the
optical access or else may already be fulfilled if it relates only
to a portion of the spatial extension of the optical access, for
example, if, as viewed from the overflow opening, the optical
access is partly visible and partly covered by the means.
[0039] It may be advantageously provided in accordance with an
example embodiment of the present invention that the outlet opening
is formed at an end face of the protective tube module directed
away from the housing body, and that the inlet opening, as viewed
from the optical access, is situated in front of the outlet opening
in the direction pointing from the optical access to the outlet
opening. In other words, therefore, the outlet opening is situated
at a distal end of the protective tube module or of the particle
sensor, the at least one inlet opening is situated proximally from
the outlet opening. Such an arrangement ensures in the case of the
arrangement of the particle sensor within a flow channel that a
measuring gas flow has a higher velocity at the location of the
outlet opening than at the location of the inlet opening. The
static pressure is then higher at the location of the inlet opening
than at the location of the outlet opening and the sub-flow flows
through the interior of the protective tube module or of the
particle sensor starting from the inlet opening toward the outlet
opening.
[0040] Multiple inlet openings may also be provided. For example, 6
to 12 inlet openings may be provided. These may be partially or
collectively situated at the same level in the direction pointing
from the optical access to the outlet opening. What was said within
the scope of the application for the inlet opening applies to
multiple or to all of these inlet openings. Alternatively, the
inlet opening may also be designed as the open orifice of an
annular gap present between the first protective tube and the
second protective tube.
[0041] Multiple overflow openings may also be provided. For
example, 4 to 12 overflow openings may be provided. These may be
partially or collectively situated at the same level in the
direction pointing from the optical access to the outlet opening.
What was said within the scope of the application of the overflow
opening applies to multiple or to all of these overflow
openings.
[0042] It may be advantageously provided that the inlet opening, as
viewed from the optical access, is situated behind the overflow
opening in the direction pointing from the optical access to the
outlet opening. Such an arrangement ensures that the sub-flow flows
initially in the direction toward the optical access. Once
redirected, it may be directed to the laser focus and subsequently
exit the protective tube module through the outlet opening.
[0043] The laser focus is advantageously situated outside the area
fluidically shielded by the sub-flow. Instead, it is situated, in
particular, in an area flowed against by the sub-flow.
BRIEF DESCRIPTION OF THE DRAWINGS
[0044] Exemplary embodiments of the present invention are
represented in the figures and are explained in greater detail
below. Identical reference numerals in various figures each
identify elements that are identical or at least comparable in
function.
[0045] FIG. 1 shows an illustration of the measuring principle
based on the laser-induced incandescence, which is preferably used
in an example embodiment of the present invention.
[0046] FIG. 2 shows a basic structure for illustrating the
operating mode of the sensor.
[0047] FIG. 3 shows by way of example a basic structure of a
particle sensor according to an example embodiment of the present
invention.
[0048] FIGS. 4a, 4b and 4c show three variants of a first exemplary
embodiment of the present invention.
[0049] FIGS. 5a, 5b, and 5c show three variants of a second
exemplary embodiment of the present invention.
[0050] FIG. 6 shows a third exemplary embodiment of the present
invention.
DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS
[0051] FIG. 1 illustrates a measuring principle based on the
laser-induced incandescence. High-intensity laser light 10 strikes
a particle 12, for example, a soot particle. The intensity of laser
light 10 is so high that the energy of laser light 10 absorbed by
particle 12 heats particle 12 to several thousand degrees Celsius.
As a result of the heating, particle 12 emits significant radiation
14 in the form of thermal radiation spontaneously and essentially
in no preferred direction. A portion of radiation 14 emitted in the
form of thermal radiation is therefore also emitted opposite to the
direction of incident laser light 10
[0052] FIG. 2 schematically shows a basic structure for
illustrating the operating mode of particle sensor 16. Particle
sensor 16 includes here a laser 18 designed as a CW laser module
(CW: continuous wave), the preferably collimated laser light 10 of
which is focused using at least one convergent lens 20 situated in
the beam path of laser 18 to a very small focus 22, in which the
intensity of laser light 10 is sufficiently high for laser-induced
incandescence. The present invention is not limited to the use of a
CW laser. It is also possible to use pulsed-operated lasers.
[0053] The dimensions of spot 22 are in the range of several .mu.m,
in particular in the range of at most 200 .mu.m, so that particles
12 crossing spot 22 are excited for emitting evaluatable radiation
power, whether it be through laser-induced incandescence or through
chemical reactions (in particular, oxidation). As a result, it may
usually be assumed that a particle 12 is always located in spot 22
and that an instantaneous measuring signal of particle sensor 16
originates only from this at most one particle 12. The measuring
signal is generated by a detector 26, which is situated in particle
sensor 16 in such a way that it detects radiation 14, in
particular, thermal radiation originating from particles 12
transiting through spot 22. For this purpose, detector 26
preferably includes a photodiode 26.1. A single particle
measurement thus becomes possible which, in principle, even enables
the extraction of pieces of information about particle 12 such as
size and velocity.
[0054] FIG. 3 shows by way of example a basic structure of a
particle sensor 16 according to the present invention.
[0055] Particle sensor 16 includes an arrangement made up of a
first outer protective tube 210 and a second inner protective tube
220. The arrangement is only roughly and schematically shown here,
reference is made in this respect to FIGS. 4, 5 and 6.
[0056] Particle sensor 16 includes a laser 18, which generates
preferably collimated laser light 10. A beam splitter 34 is located
in the beam path of laser light 10. A portion of laser light 10
passing through beam splitter 34 without deflection is focused by
convergent lens 20 to a very small focus 22. In this focus 22, the
light intensity is high enough to heat particles 12 transported
with exhaust gas 32 to several thousand degrees Celsius so that
heated particles 12 emit significant radiation 14 in the form of
thermal radiation. This radiation 14 is in the near-infrared and
visible spectral range, for example, without the present invention
being limited to radiation 14 from this spectral range. A portion
of this undirected radiation 14 emitted in the form of thermal
radiation, is detected by convergent lens 20 and directed via beam
splitter 34 to detector 26. This structure has the advantage that
only one optical access 40 to exhaust gas 32 is required, since the
same optical system, in particular, the same convergent lens 20, is
used for generating focus 22 and for detecting radiation 14
emanating from particle 12. Exhaust gas 32 is one example of a
measuring gas. The measuring gas may also be another gas or a gas
mixture, for example, ambient air.
[0057] Laser 18 includes a laser diode 36 and a second lens 38,
which preferably collimates laser light 10 emanating from laser
diode 36. The use of laser diode 36 represents a particularly
cost-effective and easily manageable option for generating laser
light 10. The preferably collimated laser light 10 is focused by
convergent lens 20.
[0058] Optical particle sensor 16 includes a first part 16.1
(exhaust gas side) exposed to the exhaust gas and a second part
16.2 (clean gas side) not exposed to the exhaust gas, which
contains the optical components of particle sensor 16. Both parts
are separated by a separating wall 16.3, which extends between
protective tubes 210, 220 and the optical elements of particle
sensor 16. Wall 16.3 serves to insulate the sensitive elements from
exhaust gas 32. Mounted in separating wall 16.3 in the beam path of
laser light 10 is an optical access 40 designed as a window,
through which laser light 10 enters into exhaust gas 32, and via
which radiation 14 emanating from focus 22 is able to strike
convergent lens 20 and from there detector 26 via beam splitter
34.
[0059] As an alternative to the exemplary embodiment described
herein, the generation of focus 22 and the detection of radiation
14 emanating from particles in focus 22 may take place via
separated optical beam paths.
[0060] It is also possible to generate focus 22 using lens
combinations other than those specified herein merely as an
exemplary embodiment. Moreover, particle sensor 16 may also be
implemented using laser light sources other than laser diodes 36
specified herein for exemplary embodiments.
[0061] FIG. 4a shows a first exemplary embodiment of the present
invention. In this case, the components situated in second part
16.2 not exposed to the exhaust gas are omitted in FIG. 4a for
better clarity. Reference may be made in this regard to FIG. 3.
[0062] Particle sensor 16 includes a housing 100, which is
assembled of a housing body 300 and a protective tube module 200
fixed on housing body 300 on the exhaust gas side.
[0063] Housing body 300 is in turn assembled of a cylindrical
housing body sleeve 310 and a cap screw 320 slidable onto housing
body sleeve 310.
[0064] Housing body sleeve 310 includes a through-channel 311,
which is sealed in a gas-tight manner on the side facing the
exhaust gas by an optical window, which forms the optical access
40. Thus, second part 16.2 of particle sensor 16 not exposed to the
exhaust gas is situated on the side of optical access 40 facing
away from the exhaust gas.
[0065] Housing body sleeve 310 further includes a circumferential
annular support element 312 at its end facing the exhaust gas, the
exhaust gas side of which is provided for installing in a
connecting piece, for example, of an exhaust gas tract. The side of
support element 312 facing away from the exhaust gas is acted upon
by cap screw 320. The lateral area of cap screw 320 includes an
external thread 323 and a hexagonal profile 322, so that particle
sensor 16 is fixable, for example, in an exhaust tract of an
internal combustion engine.
[0066] Protective tube module 200 is fixed in part 16.1 of particle
sensor 16 exposed to the exhaust gas on housing body sleeve 310 on
the exhaust gas side of support element 312. Protective tube module
200 in this example is made up of a first protective tube 210, a
second protective tube 220 and a third protective tube 230.
[0067] First protective tube 210 has a pot-shaped design, including
a pot rim 211 which is fastened, for example, welded at support
element 312 of housing body sleeve 310. First protective tube 210
further includes a pot wall 212 forming a lateral area and a pot
base 213. A circumferential ring of holes made up, for example, of
12 inlet openings 101 of particle sensor 16 is formed in pot wall
212 close to pot base 213.
[0068] Second protective tube 220 has an essentially hat-shaped
design and is situated essentially in the interior of first
protective tube 210. Second protective tube 220 abuts with a
circumferential radial flange section 221 axially against support
element 312 of housing body sleeve 310 and radially against the
interior side of pot wall 212 of first protective tube 210. An
overflow opening section 223 of second protective tube 220 tapered
via an annular step 222 is connected to radial flange section 221
of second protective tube 220. A ring of holes made up of, in the
example, 12 overflow openings 103 is provided in overflow opening
section 223, which connect an annular space 240 formed between
first protective tube 210 and second protective tube 220 to a gas
space 250 formed in the interior of second protective tube 220. A
conically tapering area 224 is connected to overflow opening
section 223 of second protective tube 220, and connected to this is
a cup-shaped end area 225 of second protective tube 220, which is
pressed with its lateral area 225.1 into an opening in pot base 213
of first protective tube 210. Outlet opening 102 of particle sensor
16 which, in the present example, is only slightly smaller than end
face 225.2 itself, is provided in end face 225.2 of end area 225 of
second protective tube 220.
[0069] Third protective tube 230 is in turn situated in the
interior of second protective tube 220. It includes a first,
straight cylindrical section 231, with which it is pressed into an
opening 312.1 of support element 312. A conically tapering section
232, which is open on side 233 of third protective tube 230 facing
the exhaust gas is connected to straight cylindrical section 231 of
third protective tube 230.
[0070] Conically tapering section 232 of third protective tube 230
is situated at the same axial level as overflow openings 103 in
second protective tube 220 along an axial direction 400, which is
defined, for example, by the direction pointing from optical access
40 to outlet opening 102.
[0071] As a result of the structure of particle sensor 16 and, in
particular, of housing 100, a sub-flow 321 is removable from a flow
of an exhaust gas 32, which initially enters through inlet openings
101 of particle sensor 16 situated in first protective tube 210
into an annular space 240 situated between first protective tube
210 and second protective tube 220, from where it enters through
overflow openings 103 in second protective tube 220 into gas space
250 situated in the interior of second protective tube 220, is
redirected there by conically tapering section 232 of third
protective tube 230 and finally exits second protective tube 220
and thus protective tube module 200 again through outlet opening
102.
[0072] The redirection at conically tapering section 232 of third
protective tube 230 ensures that sub-flow 321 does not arrive at
optical access 40. In this respect, the latter is situated in an
area 500 shielded from sub-flow 321. Particles 12 potentially
contained in exhaust gas 32 are thus unable to contaminate optical
access 40.
[0073] FIG. 4b shows one variant, in which inlet openings 101 of
particle sensor 16 are not formed as simple holes, but as holes
provided with swirl flaps 101.1. Swirl flaps 101.1 are configured
in such a way that they impose on sub-flow 321 entering into
annular space 240 a flow direction, which has one portion that is
tangential to lateral area 212 of first protective tube 210 and
further has a portion that is directed to housing body 300, i.e.,
downward in FIG. 4b.
[0074] Inlet opening 101 as a combination of hole and associated
swirl flap 101.1 may, for example, be manufactured by cutting or
pressing sections of first protective tube 210.
[0075] FIG. 4c shows a variant different from particle sensor 16
shown in FIG. 4a. The difference is that inlet openings 101 are not
formed in pot wall 212 of first protective tube 210, but are formed
on a ring of holes in pot base 213 of first protective tube
210.
[0076] FIG. 5a shows a second exemplary embodiment of the present
invention. In this case, the components situated in second part
16.2 not exposed to the exhaust gas are omitted in FIG. 5a for
better clarity. Reference may be made in this regard to FIG. 3.
[0077] Particle sensor 16 includes a housing 100, which is
assembled of a housing body 300 and a protective tube module 200
fixed on the exhaust gas side on housing body 300.
[0078] Housing body 300 in turn is assembled of a cylindrical
housing body sleeve 310 and a cap screw 320 slidable onto housing
body sleeve 310.
[0079] Housing body sleeve 310 includes a through-channel 311,
which is sealed in a gas-tight manner on the side facing the
exhaust gas by an optical window, which forms optical access 40.
Thus, second part 16.2 of particle sensor 16 not exposed to the
exhaust gas is situated on the side of optical access 40 facing
away from the exhaust gas.
[0080] Housing body sleeve 310 further includes at its end facing
the exhaust gas a ring-like circumferential support element 312,
the side on the exhaust gas side being provided for installation in
a connecting piece, for example, of an exhaust tract. The side of
support element 312 facing away from the exhaust gas is acted upon
by cap screw 320. The lateral area of cap screw 320 includes an
external thread 323 and a hexagonal profile 322, so that particle
sensor 16 is fixable, for example, in an exhaust tract of an
internal combustion engine.
[0081] Protective tube module 200 is fixed in part 16.1 of particle
sensor 16 exposed to the exhaust gas at housing body sleeve 310 on
the exhaust gas side of support element 312. Protective tube module
200 in this example is made up of a first protective tube 210 and a
second protective tube 220.
[0082] First protective tube 210 has a pot-shaped design including
a pot rim 211, which is attached, for example, welded, at support
element 312 of housing body sleeve 310. First protective tube 210
further includes a pot wall 212 forming a lateral area. Pot wall
212 tapers in a step-like manner above a ring-shaped shoulder
surface 216. A connecting conically tapering section 217 includes a
central opening on the end face, which represents outlet opening
102 of particle sensor 16.
[0083] Second protective tube 220 has essentially the shape of a
step-like sleeve open on both sides. It is situated in the interior
of first protective tube 210. Second protective tube 220 abuts with
a circumferential radial flange section 221 axially against support
element 312 of housing body sleeve 310 and radially against the
inner side of pot wall 212 of first protective tube 210. An
overflow opening section 223 of second protective tube 220 tapered
via an annular step 222 and essentially cylindrical is connected to
radial flange section 221 of second protective tube 220. A ring of
holes made up of, in the example, 8 overflow openings 103 is
provided in overflow opening section 223, which connect an annular
space 240 formed between first protective tube 210 and second
protective tube 220 to a gas space 250 formed in the interior of
second protective tube 220.
[0084] Overflow openings 103 are designed as holes that include
swirl flaps 103.1, swirl flaps 103 imposing on sub-flow 321
entering from annular space 240 into gas space 250 a direction
oriented away from the optical access and toward outlet opening
102.
[0085] An overflow opening 103 as a combination of hole with
associated swirl flap 103.1 may, for example, be manufactured by
cutting or pressing sections of second protective tube 220.
[0086] Second protective tube 220 in this example comes into a
sealing and planar contact 223.2 with end section 223.1 of its
overflow opening section 223 facing the exhaust gas in the tapered
section of pot wall 212 of first protective tube 210.
[0087] As a result of the structure of particle sensor 16 and, in
particular, of housing 100, a sub-flow 321 is removable from a flow
of an exhaust gas 32, which initially enters through inlet openings
101 of particle sensor 16 situated in first protective tube 210
into an annular space 240 situated between first protective tube
210 and second protective tube 220, from where it enters through
overflow openings 103 in second protective tube 220 into gas space
250 situated in the interior of second protective tube 220. When
passing through overflow openings 103, a direction is imposed on
it, which is oriented away from optical access 40, upward in FIG.
5a. In this regard, optical access 40 is in an area 500 shielded
from sub-flow 321. Particles 12 potentially contained in exhaust
gas 32 are thus unable to contaminate optical access 40.
[0088] FIG. 5b shows one variant, in which inlet openings 101 of
particle sensor 16 are not formed as simple holes, but as holes
provided with swirl flaps 101.1. Swirl flaps 101.1 are configured
in such a way that they impose on sub-flow 321 entering into
annular space 240 a flow direction, which has a portion tangential
to lateral area 212 of first protective tube 210 and further has a
portion, which is directed to housing body 300, i.e., downward in
FIG. 5b.
[0089] Inlet opening 101 as a combination of hole including
associated swirl flap 101.1 may, for example, be manufactured by
cutting or pressing sections of first protective tube 210.
[0090] FIG. 5c shows another variant of particle sensor 16
different from that shown in FIG. 5a. The difference is that inlet
openings 101 are not formed in pot wall 212 of first protective
tube 210, but are formed on a ring of holes in pot base 213 of
first protective tube 210.
[0091] FIG. 6 shows a third specific embodiment of the present
invention. In this case, the components situated in second part
16.2 not exposed to the exhaust gas are omitted in FIG. 6 for
better clarity. Reference may be made in this regard to FIG. 3.
[0092] Particle sensor 16 includes a housing 100, which is
assembled of a housing body 300 and a protective tube module 200
fixed at housing body 300 on the exhaust gas side.
[0093] Housing body 300 includes a through-channel 311, which is
sealed in a gas-tight manner on the side facing the exhaust gas by
an optical window, which forms optical access 40. Thus, second part
16.2 of particle sensor 16 not exposed to the exhaust gas is
situated on the side of optical access 40 facing away from the
exhaust gas.
[0094] The lateral area of housing body 300 includes, for example,
an external thread 323 and a hexagonal profile 322, so that
particle sensor 16 is fixable, for example, in an exhaust tract of
an internal combustion engine.
[0095] Protective tube module 200 is fixed at housing body 300 on
the exhaust gas side in part 16.1 of particle sensor 16 exposed to
the exhaust gas. Protective tube module 200 in this example is made
up of a first protective tube 210 and a second protective tube
220.
[0096] First protective tube 210 has a pot-shaped design, including
a pot rim 211, which is fastened, for example, welded, at housing
body 300. First protective tube 210 further includes a pot wall 212
forming a lateral area.
[0097] Second protective tube 220 has an essentially hat-shaped
design and is situated essentially in the interior of first
protective tube 210. Second protective tube 220 abuts with a
circumferential brim section 221' axially against housing body 300
and radially against the interior side of pot wall 212 of first
protective tube 210. A ring of holes of, in the example, 8 overflow
openings 103 is also situated in brim section 221'. Thus, overflow
openings 103 thus point in the direction of housing body 300 and
thus enable a gas exchange between annular space 240 formed between
first protective tube 210 and second protective tube 220 and a gas
space 250 formed in the interior of second protective tube 220.
[0098] A hat guard section 222' closed radially and open axially on
both sides is connected to brim section 221' of second protective
tube 220. The open end of hat guard section 222' facing the exhaust
gas forms outlet opening 102 of particle sensor 16. The open end of
annular space 240 facing the exhaust gas forms inlet opening 101 of
particle sensor 16.
[0099] At least one recess 305 is formed in the end face of housing
body 300 opposite overflow openings 103. This recess 305 redirects
a sub-flow 321 entering through an overflow opening 103, in the
example, by almost 108.degree., away from optical access 40 and
toward outlet opening 102.
[0100] It may be provided that each overflow opening 103 is
provided an individual recess 305 of the end face of housing body
300, for example, a bowl-shaped recess 305, for example, with a
round cross section in top view. However, it may also be provided
that a single recess 305 in the form of a single circumferential
groove is provided in the end face of housing body 300, which is
situated opposite all overflow openings 103 together.
[0101] As a result of the structure of particle sensor 16 and, in
particular, of housing 100, a sub-flow 321 is removable from a flow
of an exhaust gas 32, which initially enters through inlet opening
101 of particle sensor 16 situated in first protective tube 210
into an annular space 240 situated between first protective tube
210 and second protective tube 220, from where it enters through
overflow openings 103 in second protective tube 220 into gas space
250 situated in the interior of second protective tube 220.
[0102] The redirection at recess 305 in housing body 300 ensures
that sub-flow 321 does not reach optical access 40. In this regard,
optical access 40 is situated in an area 500 shielded from sub-flow
321. Particles 12 potentially contained in exhaust gas 32 are thus
unable to contaminate optical access 40.
* * * * *